We present a p-and n-doped nonacene compound, NOBNacene, that represents a rare example of a linearly extended ladder-type multiresonant thermally activated delayed fluorescence (MR-TADF) emitter. This compound shows efficient narrow deep blue emission, with a λ PL of 410 nm, full width at half maximum, FWHM, of 38 nm, photoluminescence quantum yield, Φ PL of 71 %, and a delayed lifetime, τ d of 1.18 ms in 1.5 wt % TSPO1 thin film. The organic lightemitting diode (OLED) using this compound as the emitter shows a comparable electroluminescence spectrum peaked at 409 nm (FWHM = 37 nm) and a maximum external quantum efficiency (EQE max ) of 8.5 % at Commission Internationale de l'Éclairage (CIE) coordinates of (0.173, 0.055). The EQE max values were increased to 11.2 % at 3 wt % doping of the emitter within the emissive layer of the device. At this concentration, the electroluminescence spectrum broadened slightly, leading to CIE coordinates of (0.176, 0.068).

Two multiresonant thermally activated delayed fluorescence (MR‐TADF) emitters are presented and it is shown how further borylation of a deep‐blue MR‐TADF emitter, DIDOBNA‐N, both blueshifts and narrows the emission producing a new near‐UV MR‐TADF emitter, MesB‐DIDOBNA‐N, are shown. DIDOBNA‐N emits bright blue light (ΦPL = 444 nm, FWHM = 64 nm, ΦPL = 81%, τd = 23 ms, 1.5 wt% in TSPO1). The deep‐blue organic light‐emitting diode (OLED) based on this twisted MR‐TADF compound shows a very high maximum external quantum efficiency (EQEmax) of 15.3% for a device with CIEy of 0.073. The fused planar MR‐TADF emitter, MesB‐DIDOBNA‐N shows efficient and narrowband near‐UV emission (λPL = 402 nm, FWHM = 19 nm, ΦPL = 74.7%, τd = 133 ms, 1.5 wt% in TSPO1). The best OLED with MesB‐DIDOBNA‐N, doped in a co‐host, shows the highest efficiency reported for a near‐UV OLED at 16.2%. With a CIEy coordinate of 0.049, this device also shows the bluest EL reported for a MR‐TADF OLED to date.

The 1,3,5‐triazine electron acceptor has become one of the most popular building blocks for the design of thermally activated delayed fluorescence (TADF) materials. Many TADF design strategies are first applied in compounds that contain triazines, and there are numerous examples of organic light‐emitting diodes (OLEDs) with triazine‐containing emitters that show high efficiencies and long operating lifetimes. A comprehensive review of triazine‐containing TADF emitters is provided. This review is organized according to the triazine‐derived structural motifs, such as number and position of electron‐donor groups in donor–acceptor‐type emitters, the π‐bridging linkers employed, orientation control of the transition dipole moment, and the design of chiral and through‐space charge‐transfer emitters. The structure of the compounds with their optoelectronic properties and the corresponding performance of the OLED devices is correlated.

We present a p-and n-doped nonacene compound, NOBNacene, that represents a rare example of a linearly extended ladder-type multiresonant thermally activated delayed fluorescence (MR-TADF) emitter. This compound shows efficient narrow deep blue emission, with a λ PL of 410 nm, full width at half maximum, FWHM, of 38 nm, photoluminescence quantum yield, Φ PL of 71 %, and a delayed lifetime, τ d of 1.18 ms in 1.5 wt % TSPO1 thin film. The organic lightemitting diode (OLED) using this compound as the emitter shows a comparable electroluminescence spectrum peaked at 409 nm (FWHM = 37 nm) and a maximum external quantum efficiency (EQE max ) of 8.5 % at Commission Internationale de l'Éclairage (CIE) coordinates of (0.173, 0.055). The EQE max values were increased to 11.2 % at 3 wt % doping of the emitter within the emissive layer of the device. At this concentration, the electroluminescence spectrum broadened slightly, leading to CIE coordinates of (0.176, 0.068).

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